Ignition system for internal combustion engines



'A g- 1942- I c. s. NADLER ETAL 3 K IGNITION SYSTEM FOR' lNT ENAfi COMBUSTION ENGINES- Filed Sept. 24, 1940 V r v I VENTORSQ.

ATTORN EYS I Patented Aug. 4 1942 UNITED STATES PATENT OFFICE IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINES Charles S. Nadler, Brooklyn. and Emil Kameny, Richmond Hill, N. Y., assignors to Standard Motor Products, Inc., Long Island City, N. Y a corporation of New York Application September 24, 1940, Serial No. 358,250

2 Claims.

spark of the intensity of the normal runninga considerable drop in voltage across the battery terminals. This condition continues as long as the starting switch i closed. As a result, during this period, the voltage applied to the ignition system is correspondingly reduced and in consequence the flow of current in the primary winding of the coil is of less intensity and the current induced in the secondary winding of the coil produces a weaker and thinner spark within the cylinder.

As is well known, the starting n phase is the time at which the strongest spark is required in the cylinder, because of the necessity of igniting raw, cold and over-riched gasoline mixture.

This invention isparticularly directed to affording means for maintaining an increased current through the primary winding of the coil at the moment of starting and for such period of time thereafter as is usually suflicient to allow for delay in firing. A particular feature of this invention is the arrangement whereby, when the heating resistance which serves as the control device for the thermo-responsive switch has served its purpose in opening said switch, the amount of current thereafter flowing through the heating resistance is automatically reduced so as to provide a longer life for the heating resistance and the switch and cause less drain on the battery, and at the same time to provide at least the minimum amount of heat necessary to keep the thermo-responsiveswitch open.

Referring to the drawing which forms a part of this specification:

Fi 1 shows in cross-section, and in part diagrammatically, the current limiting device which i the subject of this invention, with associated parts of the ignition circuit shown diagrammatically.

Fig. 2 is a plan view of the current limiting device, with the cover removed. v

The one terminal of a battery Ill is connected to a relatively heavy cable H, the other end of which is connected to one of the stationary contacts of a starter switch i2. The other stationary contact of starter switch I2 is connected to one terminal of the starting motor M, the other terminal of which is connected to the ground. The opposite terminal of the battery is connected to the ground, thus, afiording a circuit whereby energy is transmitted from the battery through the closed starter switch l2 and through starting' motor M and returned to ground. This circuit is closed when the internal combustion engine-is being cranked to induce combustion to begin in the cylinders.

Connected with some convenient point of the cable II is an ammeter M. The opposite terminal of the latter is connected with ignition switch [3 and the opposite terminal of the latter is, in accordance with this invention, consaid device is connected to the terminal ll of a coil 2|, the Opposite terminal [8 of which is con-- nected to one terminal of the interrupter 19. The opposite terminal of the interrupter is connected to ground, and a condenser 20 is,

bridged around the interrupter contacts in the usual well-known manner. Current flows in the circuit just described when the ignition switch I3 is closed and when the contacts of the interrupter 19 are closed.

The coil 2| contains primary and secondary windings, the latter being connected to the primary circuit at one end and at the other end being connected to a terminal 22 from which high tension cable 23 leads to a distributor 24.

The current-limiting device interposed between terminals l5, l6, comprises a current-limiting resistor 25 directly connected between terminals l5 and I5 and normally adapted to conduct current from terminal l5 to terminal [6 through a path having a desired resistance. During the normal running of the engine, after the starting-period, current from'battery I0 is adapted to flow through current-limiting resistor 25 and thus to the primary winding of coil 2!. The IR drop in resistor 25 is such as to limit the amount of current across the points IE! to the desired amount, In relation to ground, there i a fall from terminal l5 to terminal l6 through a path of less resistance than the resistance oi currentlimiting resistor 25. Such path is aflorded by the thermo-responsive switch indicated generally by the reference character 26, comprising a stationary contact 21, and a movable contact 28 secured upon a movable and flexible switch member 29 whose opposite end 30 is secured by a rivet 3| upon the rim of an annular ring 32 of insulating material. Also secured under the head of rivet 3|, and in conductive relation to the end 30', is a strap 35 which projects outwardly from ring 32 and serves as the terminal l6. Fixed contact 21 is mounted upon a bridging member 33 which has a projecting lug serving as the terminal I5 and is secured upon ring 32 by rivet 34.

Thus, when contacts 21, 28 are in engagement, current will flow from terminal l5 through the switch members to terminal IS. The path thus described is of little or no substantial resistance to the current and is in parallel with currentlimiting resistor 25. When current flows from terminal I5 to terminal l6 through the closed switch, there is no substantial difierence between the potential of terminal and the potential of terminal I6, in relation to ground. Upon the opening of this switch, current passes through the resistor 25 and the difference in potential due to the IR drop in that resistor is thus brought about.

For the actuation of thermo-responsive switch 26, we provide a heating coil 36 consisting of a tightly wound spiral of suitable metal coiled within annular ring 32 and closely juxtaposed to a bimetallic element 31 loosely fltted within a circular channel in the inner face of ring 32. A connecting rod 36 interconnects bimetallic element 31 and flexible switch member 29. Preferably, a disk 39 of insulating material, having a central opening for the connecting rod 36 is seated upon a suitable shoulder of the ring 32 and forms a small chamber within which heating resistance 36 is enclosed.

For our purpose, the form or design of the thermo-responsive switch member is unimportant except that the heating resistance 36 shall be in close thermal relationship with bimetallic element 31 and both shall be sumciently shielded from the temperature of the ambient air so that the temperature of the latter shall not greatly affect the length of time within which switch 26 opens after heating resistance 36 has been energized.

Heating resistance 36 is interconnected between terminal i6 and ground. The eflect of this arrangement will be apparent from the statement of operation which follows.

The operationis as follows: Normally, when the engine is not running, and the ignition switch I3 is open, the arrangement of the bimetallic element 31 is such that switch 26 remains closed. Accordingly, when ignition switch 13 is closed, current will flow from battery ID to terminal l5 and thence across the closed points of switch 26 potentialof terminal l5 and is substantially the full available voltage of the battery.

The size, nature of the bimetallic unit 31, and the relationship of the parts within ring 32 are such as to provide for the opening of thermoresponsive switch 26 after full current has been flowingthrough heating resistance 36 for a period of approximately twenty seconds. If desired, the design of these parts can be such as to make the period shorter or longer as desired. We believe that twenty seconds is sufliciently long, in the average case, to permit cranking and starting of the engine. Periods substantially longer than twenty seconds during which the full voltage of the battery is impressedacross the points l9 might create damage to the latter.

When the heating of resistance 36 causes bimetallic element 31 to snap downwardly (as seen in Fig. 1), switch points 21, 26 open and the direct current path therethnough from terminal l5 to terminal I6 is broken. Thereupon, current flows from terminal I5 to terminal l6 through the current-limiting resistor 25. This arrangement persists during the balance of the time that the engine is running, resulting in a reduction in the voltage applied across the points l9 and a limiting of the amount of current flowing through the primary circuit. At the same time, the potential of terminal I6 in relation to ground becomes less than the potential of terminal l5, due to the IR drop in resistor 25. Accordingly, the potential impressed across heating resistance 36 falls and in consequence less current flows through heating resistance 36.

We prefer to select such a value for resistor 25 as to bring about a limitation of approximately 10% to 15% in the amount of current passing through the primary circuit, but our invention includes current limitation of substantially greater or less value if desired. By connecting the heating resistance 36 to terminal l6, 9. like reduction is brought about in the amount of current passing through heating resistance 36, and yet at the same time heating resistance 36 is not in series with the primary winding of the coil or the points l9, as in prior devices. The characteristics of bimetallic unit 31 are so selected that after the fully energized heating coil 36 has opened switch 26, the reduced energization of heating coil 36 is sufllcient to keep switch 26 open.

By'the arrangement disclosed, the time interval which elapses between the closing of ignition switch l3 and the cutting in of current-limiting resistor 25 can be made substantially independent of factors of variability inherent in prior systems and in addition, the reduction in the energization of heating coil 36 which accompanies the cutting in of current-limiting resistor 25 results in longer life for the heating resistance 36 and its associated bimetallic unit, and less drain on the battery during running of the motor.

While we have for convenience disclosed herein a specific form of thermo-responsive switch mounted within an annular ring 32 of insulating material, we do not believe that our invention is limited to .the specific structure shown, but intend that the scope oi this invention shall be as set forth in the subjoined claims.

We claim:

1. For use in an ignition system which contains a source of electrical current and the primary winding of a coil, the combination of a current-limiting resistor adapted, when the thermo-responsive switch hereinafter mentioned is open, to be connected across the source of current in series with said primary winding, a thermo-responsive switch connected in parallel with said resistor and when closed conducting current from said source to said primary winding through a path of substantially less resistance 3 than said resistor, and a heating resistance in thermal relationship with said thermo-responsive switch and adapted, when said thermo-responsive switch is open, to be connected across the source of current in series with the currentlimiting resistor and in parallel with the primary winding of the coil.

2. For use in an ignition system, a currentlimiting device comprising a current-limiting resistor, a theme-responsive switch connected across the ends of said current-limiting resistor,

. and a heating resistance positioned in thermal relationship -.with said switch and adapted tobe connected between ground-and that end of said current-limiting resistor which is adapted to operate at the lower potential.

' CHARLES S.- NADLER. 

